The incident occurred a few days before Erdogan is set to travel to Germany for a G20 summit, and after German officials rejected a request by the Turkish president to address ethnic Turks in Germany.

Activists of the “Attac” network wear masks of (L-R) French President Emmanuel Macron, Turkish President Recep Tayyip Erdogan, US President Donald Trump, German Chancellor Angela Merkel, Britain’s Prime Minister Theresa May, and Russian President Vladimir Putin as they demonstrate in Hamburg, northern Germany, on July 4, 2017.

Relations have soured between Berlin and Ankara since a failed coup in Turkey in July last year. Germany has repeatedly criticized Turkey for a massive crackdown that was launched right after the coup, saying the action has been carried out beyond the rule of law.

The two countries have also clashed on several other issues, including Germany’s alleged support for Kurdish opponents and a referendum in Turkey last April, which gave Erdogan sweeping new powers.

Germany is home to some three million ethnic Turks. The country allowed in the Turks in the 1960s and 1970s as part of its massive post-war “guest worker” program. Erdogan held his last speech to members of the community in May 2015 in the city of Karlsruhe.